A quantum dot (QD) is a semiconductor nanoparticle. The quantum dot having a nanometer size emits light while electrons in an unstable state fall from a conduction band to a valence band, light having a short wavelength is emitted as the size of the particle of the quantum dot is reduced, and light having a long wavelength is emitted as the size of the particle is increased. Accordingly, if the size of the quantum dot is adjusted, a visible ray having a desired wavelength may be exhibited, and various colors may be implemented simultaneously by using the quantum dots having various sizes.
A desired natural color may be implemented, a color reproduction range is good, and luminance is favorable by controlling the size of the quantum dot, and thus, lighting devices comprising the quantum dot have received attention as a next-generation device.